ARTICLE Two new of typically Amazonian lineages in the Upper Rio (: Hoplomyzontinae and : ), with a biogeographic discussion

Fernando Cesar Paiva Dagosta¹ & Mário de Pinna²

¹ Universidade Federal da Grande Dourados (UFGD), Faculdade de Ciências Biológicas e Ambientais (FCBA). Dourados, MS, Brasil. ORCID: http://orcid.org/0000-0001-7163-296X. E‑mail: [email protected] (corresponding author) ² Universidade de São Paulo (USP), Museu de Zoologia (MZUSP). São Paulo, SP, Brasil. ORCID: http://orcid.org/0000-0003-1711-4816. E‑mail: [email protected]

Abstract. Two new species of particular biogeographic significance are described from the upper rio Paraguay basin, one of the Paracanthopoma (Trichomycteridae, Vandelliinae) and the other of the genus Ernstichthys (Aspredinidae, Hoplomyzontinae). The two species occur sympatrically in the Rio Taquarizinho, tributary of the Rio Taquari, in the upper Paraguay system. Paracanthopoma saci is distinguished from its only congener, P. parva, by a spatulate caudal peduncle; a minuscule premaxillary dentition (reduced to three delicate teeth); the supraorbital latero-sensory canals opening as two separate s6 pores; the caudal fin slightly convex or truncate with round edges; the skull roof entirely open, unossified; the origins of dorsal and anal fins approximately at same vertical; and the pelvic fin with three rays. Ernstichthys taquari is diagnosed among congeners by the narrow bony shields on dorsal and ventral series, not overlapping or contacting each other; by the presence of seven or eight serrations on the posterior margin of the pectoral spine; and by the pectoral-fin spine only slightly larger than subsequent soft rays. Both Paracanthopoma and Ernstichthys were previously unknown outside of the Greater Amazonian river systems (Amazon, , Essequibo and smaller surrounding drainages). Their presence restricted to the Rio Taquari is unexpected and suggests a peculiar biogeographical history. Ancestral geographic distributions were reconstructed using S‑DIVA and BBM methods in RASP. A majority of resulting hypotheses support that the two species reached the Paraguay from the Amazon. The alternative explanation accounts for their presence in the Paraguay by vicariant events. In no case, their presence in the Paraguay is an ancestral distribution with subsequent Amazonian dispersal. Though unusual, this pattern is also seen in a few other fish taxa, showing that the Rio Taquari is biogeographically hybrid, combining elements from both the Paraguay and Amazon drainages.

Keywords. Systematics; Ichthyology; Biogeography; ; ; Siluriformes; Paracanthopoma; Ernstichthys.

INTRODUCTION 2018; Albert et al., 2020). Because fishes have ex- tremely limited dispersal abilities across land, the Historical biogeography, like most historical ichthyofaunal composition of a basin is an imprint sciences, is a discipline that studies the past and of its history with other basins. However, such therefore is not optimized for formulating predic- historical portrait is both complex and imperfect. tions about the future (Morrone, 2009). On the Complex due to its temporally mixed context and other hand, historical biogeography is efficient in imperfect because biological events such as dis- making retrodictions, i.e., to “predict” past events persal, hybridization and extinctions tend to be (Morrone, 1997, 2009). Of course, its predictions blurred with time. Temporal mixing results from apply to not-yet-known results of past events. overlapping geomorphological processes that With progress in knowledge about phylogenet- cause hydrological mixing between neighboring ic relationships and distribution of Neotropical basins (i.e., connection, diversion, sector capture, fishes, it becomes increasingly clear how geomor- etc.). Consequently, basins present a mosaic of phological past events shaped ichthyological di- fish assemblages composed of elements from versity (Albert & Reis, 2011; Dagosta & de Pinna, different geographic origins recruited across dif-

Pap. Avulsos Zool., 2021; v.61: e20216147 ISSN On-Line: 1807-0205 http://doi.org/10.11606/1807-0205/2021.61.47 ISSN Printed: 0031-1049 http://www.revistas.usp.br/paz ISNI: 0000-0004-0384-1825 http://www.scielo.br/paz Edited by: Carlos José Einicker Lamas http://zoobank.org/31481179-ADAD-48BF-BD7E-F326BEE7999A Received: 18/03/2021 Accepted: 12/04/2021 Published: 19/04/2021 Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 2/23 ferent times and events (Lima & Ribeiro, 2011; Dagosta The Hoplomyzontinae is the rarest and least known et al., 2014; Dagosta & de Pinna, 2017). aspredinid subfamily. The first described member of the Herein we discuss the evidence and underlying caus- group was atrizona Myers, 1942 and rec- es for two new siluriforms which are particularly elo- ognition of a suprageneric taxon came with Fernández- quent testimonies of Amazonian affinities of the upper Yépez (Fernández-Yépez, 1953). Additional diversity has rio Taquari, rio Paraguay basin. The first one is a para- been slow in forthcoming and collections of hoplomy- sitic catfish of the genus Paracanthopoma, of subfamily zontines are still rare. However, there is evidence that Vandelliinae, family Trichomycteridae. The second one their abundance and ecological relevance may be far is an Ernstichthys, of subfamily Hoplomyzontinae, fam- larger than current sparse museum collections seem to ily Aspredinidae. Both taxa belong to previously exclu- suggest (Taphorn & Marrero, 1990). The subfamily con- sive-Amazonian-core lineages (Paracanthopoma and tains Dupouyichthys Schultz, 1944 (1 sp.), Ernstichthys Hoplomyzontinae, respectively) and were collected sym- Fernández-Yépez, 1953 (3 spp.), Hoplomyzon Myers, 1942 patrically and syntopically in the Rio Taquari. (4 spp.), and Micromyzon Friel & Lundberg, 1996 (2 spp.) The Vandelliinae includes the only exclusively hema- and all its species are small-sized. The morphology of tophagous gnathostomes besides vampire bats. Their ev- hoplomyzontines is aberrant, with several adaptations er-lasting popular fame stems from their occasional and unique among siluriforms, including a complex body accidental penetration of natural openings of the human armor composed of shield- and plate-like modifications body (Spotte, 2002). Vandelliines feed exclusively on derived from different skeletal elements. Despite being blood as adults, a behavior that is general for all species such an obvious object of interest for morphological in- in the group. Normally they enter the gill cavity of prey vestigation, the anatomy of Hoplomyzontinae remained fishes, lacerate a blood vessel, gorge on blood and leave, poorly-known until recently, with fragmentary informa- but variant strategies are known to exist across the taxo- tion scattered in various publications. This situation be- nomic diversity of the group, although as yet poorly un- gan to change with Carvalho et al. (2016) and Carvalho derstood (Kelley & Atz, 1964; Zuanon & Sazima, 2004). The et al. (2017) which offered an unprecedented picture of Vandelliinae comprises four genera: Paracanthopoma, the osteology of Micromyzon orinoco and Hoplomyzon , , and (a fifth genus cardosoi. Hoplomyzontine taxonomy is relatively tidy, with four new species is currently under description as might be expected for such a small group, but some by the authors). The subfamily as a whole occurs in the generic limits are based on rather limited character ev- Amazon, Orinoco, Essequibo, Magdalena, and Parana- idence. Phylogenetically, while monophyly of hoplomy- Paraguay, but its center of diversity is by far the Amazon, zontines is unchallenged and extremely well-supported where all genera and a majority of species are found. (Friel, 1994; Cardoso, 2008; Carvalho et al., 2018), their Actually, as yet only two species of Vandelliinae are relationships within Aspredinidae are still controver- known to occur outside the Amazon-Orinoco-Essequibo sial. Some studies support the genus as sister realm, both of Paravandellia: P. oxyptera Miranda-Ribeiro, group to Hoplomyzontinae (Friel, 1994) while some oth- 1912 from La Plata and Amazon and P. phaneronema ers place the subfamily as sister group to different sub- (Miles, 1943) from the Rio Magdalena basin. sets of aspredinids (Cardoso, 2008; Carvalho et al., 2018). Paracanthopoma currently comprises a single de- Proposals of relationships within hoplomyzontines also scribed species, P. parva Giltay, 1935, but new species diverge, with some hypotheses placing Hoplomyzon in the process of description will increase that diversity as sister group to the rest of the subfamily, with by an of magnitude (de Pinna & Dagosta, in prep.). Micromyzon as sister to Dupouyichthys plus Ernstichthys The genus is easily diagnosable by several unique mor- (Friel & Lundberg, 1996) and others with the positions of phological characteristics, among which the presence Hoplomyzon and Micromyzon switched relative to that of a free fold of integument across the isthmus, a trait one (Cardoso, 2008). whose significance is recognized since the original de- Geographically, hoplomyzontines are mostly restrict- scription of the taxon and which remains valid today. ed to Andean piedmonts in the western Amazon, west- Species of Paracanthopoma occur throughout lowlands ern Orinoco, Maracaibo and Magdalena drainages in a and uplands of the Amazon, Orinoco, and Essequibo, distribution pattern called Cis-Andean Foothills (Dagosta but were so far absent outside of those basins. Given & de Pinna, 2019). Exceptions to that pattern are the two the amount of ichthyological surveying so far conduct- lowland Amazonian and Orinocoan species of the ge- ed in the Paraná-Paraguay, São Francisco, and Coastal nus Micromyzon (Friel & Lundberg, 1996; Carvalho et al., Brazilian drainages, combined with the conspicuousness 2016) and a few isolated and taxonomically yet poorly of Paracanthopoma species and their abundance in the understood records of Ernstichthys and “Dupouyichthys” Amazon, it seemed highly unlikely that the genus oc- in lower portions of Rio Madeira (Ohara & Zuanon, 2013) curred outside the broad Amazonian realm. Still, small and of Ernstichthys in the Rio Pilcomayo in Bolivia and pockets of hidden diversity exist and herein we report on upper Rio Tocantins (Jarduli et al., 2014; Tiago Carvalho, a new species of Paracanthopoma which unexpectedly pers. comm.). In any case, the geographic distribution of surfaced in the Rio Taquari, upper Paraguay. It seems to the Hoplomyzontinae known to date seemed to be solid- be a narrowly endemic form, and is the first of its genus ly restricted to the northern basins of . The from outside the Amazon-Orinoco realm. This is the first discovery of a new hoplomyzontine species in the rio new species of Vandelliinae described since 1943. Taquari was therefore as surprising as the finding of its Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 3/23 co-occurring Paracanthopoma. Given such unusual cir- Pinna (1996), with the lacrimal being shorthand for the cumstances, it is fitting to describe them together in this compound lacrimal+antorbital (de Pinna et al., 2020). So publication, as taxonomic supplements to a discussion called “bony plates” in hoplomyzontines are anatomically on the biogeographical implications of the Amazonian heterogeneous. The lateral series is formed from expand- components of the upper Rio Paraguay. ed lateral-line ossicles, and are thus independent dermal bones. Remaining plate-like structures in the dorsal and ventral series are part of internal skeletal structures that MATERIAL AND METHODS emerge at the surface, thus not really independent der- mal plates. The term plates is thus herein reserved for el- Specimens were collected under the collecting per- ements of the lateral series, while the dorsal and ventral mit # 60634/1 issued to F.C.P.D. by the Instituto Chico series are called shields. Plates independent of both inter- Mendes de Conservação da Biodiversidade (ICMBio) of nal structures and lateral-line canals, such as in some lo- the Ministry of Environment. Fishes were anesthetized ricarioids (Callichthyidae, Scoloplacidae, ) are through Eugenol solution, according to the protocol absent in hoplomyzontines. Lists of types and compar- of Lucena et al. (2013). Standard length (SL) is given in ative material include catalog numbers followed by the millimeters. In morphometric data, subunits of the body number of specimens in alcohol, their SL range, number are expressed as percentages of SL and subunits of head of c&s specimens and respective SL range. Institutional as percentages of head length (HL). Measurements abbreviations follow Sabaj (2020). were point-to-point, taken with digital calipers to the nearest 0.1 mm, except for subunits of the head in Paracanthopoma, which were obtained with an ocular Biogeographic analyses micrometer and therefore as projections. Definitions of measurements and meristics for Paracanhopoma fol- Ancestral geographic distributions were recon- low Reis & de Pinna (2019). Odontodes were counted structed using statistical dispersal-vicariance analysis on cleared and stained (c&s) preparations, and included S‑DIVA (Yu et al., 2010) and BBM (Ali et al., 2012) in RASP odontodes that are attached to bone, or replacement (Yu et al., 2015). Those models are the only ones avail- odontodes in the process of filling in for an already de- able for ancestral reconstruction from trees without tached odontode, or an obviously empty socket which branch lengths in RASP. Trees were built in Mesquite happens to have lost both its occupant and replacement (Maddison & Maddison, 2019) and exported in Nexus odontode. Claw-like teeth were counted as those actu- format to RASP. In the case of Trichomycteridae, the ally attached to the premaxilla, with replacement teeth MTSVG clade from Ochoa et al. (2017) was supplemented and sockets mentioned separately in the description. The integument fold acros the isthmus in Paracanthopoma, Table 1. Distribution of taxa coded in S‑DIVA. Biogeographical regions: A = called a branchiostegal or branchial membrane by pre- Amazon-core; B = São Francisco and Eastern Coastal drainages; C = Paraná- vious authors, is here called a branchiostegal velum, Paraguay; D = Trans-Andean. to reflect its particular structure unique to the genus (see Discussion below). Definitions of measurements Trichomycteridae Aspredinidae for Ernstichthys follow Carvalho et al. (2015). Vertebral Listrura B AC counts include all preural vertebrae, including five in Microcambeva B Acanthobunocephalus A the Weberian apparatus for hoplomyzontines, but not Potamoglanis AC Hoplomyzon AD for Paracanthopoma, plus the terminal complex PU1+U1 Stauroglanis A Micromyzon A counted as one. The differentiated U2 of Ernstichthys (as Sarcoglanis A Ernstichthys AC Typhlobelus A chamaizelus A in other Aspredinidae) was not included in counts (de Pygidianops A A Pinna & Ng, 2004). In the description, the frequency of Tridens A A each count is provided in parentheses after the respec- Tridensimilis A Platystacus A tive count, with the count of the holotype indicated by Tridentopsis AC Xyliphius ACD an asterisk. Cleared and counterstained specimens for AB Pterobunocephalus AC comparative material were prepared according to Taylor Haemomaster A AC & Van Dyke (1985). High-resolution CT scan figures are AC Bunocephalus ABCD available at the online repository Harvard Dataverse B Amaralia AC https://dataverse.harvard.edu/dataverse/harvard, avail- Megalocentor A Dupouyichthys D able at http://doi.org/10.7910/DVN/XCXEM8 (Dagosta, A 2021). Radiographs were taken with a Faxitron digi- Pareiodon A tal x‑ray model. Number of serrations on the posteri- Acanthopoma A or margin of the pectoral spine from other species of AC Ernstichthys were taken from the literature (e.g., Ohara & Paracanthopoma saci C Zuanon, 2013; Stewart, 1985) and from material exam- Paracanthopoma parva A ined at MZUSP. Osteological observations in the new Paravandellia oxyptera AC Ernstichthys were done by computerized tomography of Paravandellia phaneronema D the holotype only. Osteological terminology follows de Vandellia A Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 4/23 with the addition of two valid species of Paravandellia. lectors as holotype, 17 Sep 2019. MZUSP 115585, 1 ex, Morphological evidence supports the genus as the sister 19.3 mm SL, , Mato Grosso do Sul, Alcinópolis, group to Paracanthopoma (DoNascimiento, 2015), and stream tributary to Rio Taquari (Rio Paraguay drain- its inclusion in the analysis is biogeographically relevant. age) at dirt road between Alcinópolis and road MS‑217 For Aspredinidae, the tree used was from Carvalho et al. (18°12 16.5 S, 53°34 13.5 W), col. O.T. Oyakawa, P. ′ ″ ′ ″ (2018), with the addition of Dupouyichthys, sister genus Camelier, M. Marinho, F. Dagosta, 26 Aug 2013. MNRJ to Ernstichthys (Friel, 1994; Friel & Lundberg, 1996) and 53559, 2 ex, 14.6­‑16,8 mm SL, from MZUSP 125626. therefore important for a biogeographic understanding of the group. Coding of terminal distributions was at the Diagnosis genus level (Table 1), except in case of Paravandellia and Paracanthopoma where relationships at species level Distinguished from the only other species of were necessary for biogeographic accuracy. Analyses in Paracanthopoma, P. parva, by: 1) short and anteriorly-dis- S‑DIVA and BBM were conducted with default settings placed opercular patch of odontodes, which leaves a (comparative analyses conducted with more aggres- large posterior free area of integument continuous with sive parameters yielded the same general results). Four the rest of the head integument around it (as a conse- biogeographical regions were defined: A = Amazon- quence of that morphology, in dorsal view the posterior core; B = São Francisco and Eastern Coastal drainages; tips of the opercular odontodes do not reach the base C = Paraná-Paraguay; D = Trans-Andean. The number of of the pectoral fin); 2) pelvic fin with three rays (vs. five); maximum ancestral areas was set to the maximum, lim- 3) opercle lacking an ascending process (vs. ascending ited by the number of regions previously determined (4 process present); 4) caudal peduncle spatulate by hy- areas each in Trichomycteridae and Aspredinidae). pertrophied series of 22‑29 (upper) and 20‑29 (lower) procurrent caudal-fin rays (vs. caudal peduncle narrow, with 15 to 19 upper and 14 to 18 lower rays); 5) median RESULTS premaxillary dentition feeble, with three delicate teeth (vs. median premaxillary dentition robust, with nine Paracanthopoma saci sp. nov. large strong teeth); 6) supraorbital canals opening as http://zoobank.org/6536E8CD-A751-4CEF-AD74-FAA3669F99D6 two separate s6 pores (vs. canals fused at midline and (Figs. 1‑2) opening as single median s6 pore); 7) caudal fin slightly convex or truncate, with round edges (Fig. 2; in Fig. 1 the Holotype: MZUSP 125624, 19.1 mm SL, Brazil, Mato apparent emarginated margin is a preservation artifact) Grosso do Sul, Alcinópolis, Rio Taquarizinho (tributary (vs. bilobed or emarginate, concave); 8) supraoccipital to Rio Taquari, Rio Paraguay drainage) (18°12 14.8 S, lacking anterior median process (vs. supraoccipital with ′ ″ 53°34 11.3 W), elev. 363 m, col. F. Dagosta, A. Ferreira, R. produced anterior process); 9) origins of dorsal and anal ′ ″ Zanon, 18 Sep 2019. fins approximately at same vertical (vs. origin of dorsal fin clearly anterior to vertical through origin of anal fin). Paratypes: MZUSP 125626, 13 ex (2 c&s), The three former characters also distinguish P. saci from 14.5‑21.8 mm SL, collected with holotype. MZUSP all undescribed species of the genus known to the au- 125622, 2 ex, 19.5‑19.9 mm SL, same locality and col- thors at this time.

Figure 1. Paracanthopoma saci, MZUSP 125624, holotype, 19.1 mm SL. Brazil, Mato Grosso do Sul, Alcinópolis, Rio Taquarizinho. (a) Lateral view, (b) Dorsal view of head, (c) Ventral view of head. Photos by V. Reis. Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 5/23

Table 2. Morphometric data of Paracanthopoma saci. Ranges, mean and SD Dorsal profile of head continuous with that of dorsum. (standard deviation) include holotype. Head subunits were obtained with an Head longer than broad, snout very broad, semicircular ocular micrometer and therefore as projections. with a continuous round anterior margin. Head muscles not entering skull roof. Head depressed (head depth ap- n holotype min max mean SD proximately 50% of head width) with dorsal profile most- Standard length (mm) 8 19.1 15.4 21.1 18.1 1.8 ly continuous from nape to tip of snout. Ventral profile of Total length 8 112.5 17.3 23.5 20.3 2.0 head straight, flattened, though externally irregular due Body depth 8 13.1 11.7 15.7 13.9 1.5 to integument folds. Eye size slightly less than one-third Caudal-peduncle length 8 25.1 24.0 26.6 25.0 1.0 of snout length, without free orbital rim, located dorsal- Caudal-peduncle depth 8 9.9 8.9 11.3 9.8 0.8 ly on head and directed dorsolaterally. Integument over Predorsal length 8 68.6 66.5 69.2 68.2 0.9 eyes thin and transparent. Center of eyes located slightly Preanal length 8 67.5 65.5 68.8 67.2 1.1 Prepelvic length 8 60.2 56.0 61.1 59.4 1.5 anterior to middle of HL, interorbital width equal to, or Dorsal-fin base length 8 9.4 6.8 10.3 8.6 1.2 slightly larger than, longitudinal diameter of eye. Eye lens Anal-fin base length 8 11 7.6 11.0 9.0 1.0 unconstricted by iris, entirely exposed on external aspect Pectoral-fin length 8 11.5 9.7 12.3 10.8 0.8 of eye. Anterior nostril small, surrounded by short tu- Head length (mm) 8 15.7 15.1 16.1 15.7 0.4 bule of integument produced posteriorly into small and Head width 8 83.6 83.6 100.0 89.2 5.1 pointed flap. Anterior internarial width slightly narrower Head depth 8 41.8 41.8 54.6 50.3 4.0 than interorbital. Posterior nares slightly larger than an- Interorbital 8 13.6 12.6 15.5 13.8 1.0 terior ones, oval (longer than broad) in shape, located Eye diameter 8 12.7 11.3 13.6 12.8 0.7 close to anteromesial margin of eyes. Center of posterior Snout length 8 36.4 35.8 39.8 37.2 1.4 nares slightly anterior to transverse line through anterior Mouth width 8 23.6 14.6 28.6 24.6 4.3 margin of eyes. Posterior internarial width slender than Anterior internarial width 8 15.5 14.6 21.8 17.2 2.4 interorbital and approximately twice as wide as antero- Posterior internarial width 8 10.9 9.7 13.6 11.0 1.2 posterior length of nostril. Opercular patch of odontodes tiny, dorsolaterally Description located on head, on dorsal half of head depth in later- al view, anterodorsally to pectoral-fin base. Opercular Morphometric data provided in Table 2. Body elon- odontodes six, disposed in two irregular rows. Odontodes gate. Cross-section of body as broad as deep at pecto- with distal portions curved medially. Opercular fold of ral-fin insertion and increasingly compressed posterior to integument vestigial or absent, instead continuous with that point, tapering to caudal fin. Dorsal profile of body large well-delimited roundish area of thickened integu- in broad gentle arc, nearly straight, from head to origin of ment resembling a vastly hypertrophied opercular fold. dorsal fin (Figs. 1‑2). Dorsal midline with transparent fin Interopercular patch of odontodes miniscule, nearly fold anterior to dorsal fin. Dorsal and ventral profiles of invisible on surface of head, located ventrolaterally on caudal peduncle straight immediately posterior to ends head, horizontally aligned with origin of pectoral fin. of dorsal and anal fins, then expanded by dorsal and Interopercular odontodes four. Interopercular patch ventral procurrent caudal-fin rays resulting in symmetri- of odontodes closer to opercular patch than to eye. cally spatulate caudal peduncle. Ventral profile of body Interopercular flap of integument absent or vestigial. nearly straight until pelvic-fin origin, but greatly distend- Mouth ventral and small, strongly flattened ven- ed in some specimens due to gut contents. Myotomes trally, delineated anteriorly and laterally by vast cres- and longitudinal skeletogenous septum clearly visible cent-shaped upper lip and posteriorly by small lower lip. through thin integument along whole body. Axillary Each premaxilla with a single claw-like tooth attached to gland large, elongate, positioned dorsal to pectoral-fin its distal tip, and one additional tooth socket with part- base and extending posteriorly approximately to mid- ly-formed tooth in parallel. Claw-like tooth deeply hidden length of adpressed pectoral fin, its large round or oval in labial tissue and difficult to expose in preserved speci- pore located at its posterior terminus. Some specimens mens without damaging soft tissue. Conical teeth absent preserved with large amount coagulated secretion still on premaxilla. Upper lip very broad but poorly-differen- attached to pore. tiated, continuous with ventral surface of snout. Median

Figure 2. Live coloration of Paracanthopoma saci. Lateral view of MZUSP 125622, 19.9 mm SL. Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 6/23 premaxilla miniscule, with three closely-set tiny teeth. slightly beyond origin of anal fin. Posterior margin of pel- Dermal pad of median premaxilla semicircular. Lower vic fin gently convex. Dorsal fin elongate, roughly trian- jaw narrow, its anterior profile M‑shaped and composed gular with roundish edge and gently convex, sinusoidal mostly of produced dentary lobes, continuous with men- or straight distal margin. Dorsal-fin rays v‑viii*+I*‑II+5-6*. tal region posteriorly. Jaw cleft short, strongly directed Anal fin similar in shape to dorsal fin, with v‑ix(viii*)+I+5 posteriorly, but curved laterally at posterior end. Dentary rays. Origin of anal fin at or slightly posterior to vertical diastema as deep median concavity between dentary through origin of dorsal-fin. Caudal fin roughly rectangu- lobes. Dentary teeth four on each side, large but difficult lar in preserved position.. Margin of caudal fin truncate to visualize in alcoholic specimens, concentrated at me- with round edges and gently convex margin (in Fig. 1 the sial end of dentary and directed anteromesially, arranged apparent emarginated margin is an artifact of the preser- in two ventral and two dorsal ones, not aligned. Dentary vation position of middle rays). Principal caudal-fin rays teeth long, their axis anteriorly-directed at base, but 5+5* or 4+5. Procurrent caudal-fin rays 22‑29 dorsally curved dorsally or dorsolaterally at distal half. Median and 20‑29 ventrally. tooth of ventral row longer than others. Vertebrae (exclusive of Weberian complex) 40 (n = 2), Branchiostegal membrane continuous posteriorly 41 (n = 3), 42* (n = 4), 43 (n = 3). First dorsal-fin pterygio- with large, continuous, posteriorly concave, free bran- phore positioned subsequent to neural spine of vertebra chiostegal velum across whole of ishtmus region. Dorsal 22 (n = 3). First anal-fin pterygiophore positioned subse- portion of branchiostegal velum reaching and slight- quent to hemal spine of vertebra 22 (n = 1) or 23 (n = 2). ly overlapping anterior margin of pectoral-fin base. Dorsal- and anal-fin pterygiophores six, poorly calcified Branchial opening small, located anteriorly to pecto- or entirely cartilaginous, clearly visible only in c&s prepa- ral-fin base, approximately equal to space between oper- rations. Branchiostegal rays three. Ribs one pair. cular and interopercular patches of odontodes. Maxillary barbel ranging from extremely short to vestigial, extend- Pigmentation in alcohol ing maximally for one-third distance between its base and base of interopercular patch of odontodes. Posterior General aspect of fish almost entirely white. Post- point of its base slightly anterior to vertical through an- orbital part of skull roof with extensive dark field formed terior margin of eye in lateral view. Rictal barbel vestigial, by brain pigment seen by transparency, its anterior mar- reduced to small knob mesially to base of maxillary one, gin strongly concave, in continuous arc or angulate, im- absent in some specimens. Nasal barbel vestigially rep- mediately posterior to eyes. Well-defined elongate dark resented by posterior elongated portion of fold around field extending anterior to eye, along lateral margin of anterior naris described above. olfactory capsule. In some specimens, mesial margin Lateral line short, approximately half of pectoral-fin of olfactory capsule also with some dark pigment, but length, and straight, extending alongside dorsal margin much weaker than lateral one. Dark pigment on body of anterior portion of axillary gland. Terminal lateral-line restricted to uniform web-like or dotted covering on dor- pore immediately dorsal to axillary gland opening. Short secondary branch splitting off ventrally from proximal sal part of abdominal wall and few isolated small spots portion of main canal, with corresponding pore opening along base of dorsal fin and, rarely, of anal and caudal anteriorly to midlength of main canal. Single lateral-line fins and muscular margins of caudal peduncle. Posterior tubule poorly calcified, extending over part of main ca- portion of vertebral column with internal dark pigment nal immediately posterior to bifurcation. on each individual vertebra, forming series of spots vis- Pectoral fin small, approximately 60% of HL, with ible externally by transparency along caudal peduncle i+4 rays in all specimens (except i+3 in one side of one (more evident in life). All fins hyaline. specimen). Pectoral-fin morphology with pronounced variation, with most specimens (n = 9, including ho- Pigmentation in life lotype) having triangular pointed shape with first ray slightly longer than others. Some specimens (n = 5) Based on Fig. 2. General body color translucent yel- with all rays equally long, resulting in truncate fin mar- lowish. Neural canal darkly pigmented along entire ver- gin. Two exceptional specimens in MZUSP 125626 (14.5 tebral column, forming continuous thin dark line along and 15.0 mm SL) with hypertrophied first pectoral-fin ray whole body. Hemal canal forming reddish line ventrally forming long filament. First ray corresponding to 36% SL along vertebral column. Limits between vertebrae from in smaller specimen and 26% SL in larger specimen, middle of abdomen to base of caudal skeleton outlined with filamentous portion approximately 2 and 1.5 times in dark by internal pigment. Branchial region pink and length of rest of fin, respectively (see Remarks below). cardiac region intense red due to blood seen by trans- Pelvic fins minute, closely set together at base, with i+2 parency. Abdomen yellow anteriorly and abruptly dark rays (with all three rays unbranched in small specimens; posteriorly due to ingested blood. Dorsal portion of ab- one specimen with vestigial additional ray posteriorly). domen with iridescent golden speckles, concentrated on Pelvic splint present in single of three c&s specimens. its anterior and posterior limits. Eggs and fatty globules Origin of pelvic fin close to origin of anal fin, well ante- faintly visible along dorsal part of abdomen. Superficial rior to vertical through origin of dorsal fin, extending integumentary dark pigmentation as described in pre- posteriorly well beyond anus and urogenital papilla and served specimens. Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 7/23

Figure 3. Distribution map of Ernstichthys spp. (open dots) and Paracanthopoma spp. (black diamonds). Red star indicates type-locality of Ernstichthys taquari and Paracanthopoma saci. Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 8/23

Ecology extreme case of filamentous pectoral-fin ray known in Trichomycteridae (where the filament is never longer The Rio Taquarizinho is ca. 15 m wide at the col- than the length of the rest of the fin). No other speci- lection locality. Water is clear, slightly milky and with mens of the species show any sign of fin elongation. The moderate current. Specimens were collected by sein- significance of this trait is difficult to interpret with the in- ing on sand banks in the middle of the river, especially formation available. The two filamentous specimens are in sectors shaded by riparian vegetation. There was no identical in all other relevant characteristics to other pu- aquatic vegetation and depth of collection ranged from tative conspecifics, there being thus no reason to suspect 30 to 150 cm. Paracanthopoma saci is sympatric with that they might represent a different taxon. At 14.5 and Paravandellia oxyptera (MZUSP 125623, 125625) with 15.0 mm SL, those two specimens are among the small- both relatively abundant at the type locality. The two spe- est known of P. saci. Sexual dimorphism in pectoral-fin cies are psammophilic, but with different microhabitat size and structure exists in all species of Paravandellia preferences. Paracanthopoma saci favors fine sand, while and some undescribed species of Paracanthopoma, with P. oxytera prefers sectors with coarser granulation. Once mature males having a stouter and larger pectoral fin, a the subtleties of their preferences are understood, it is differential particularly pronounced in the first ray (MdP, possible to target one or the other species for collection pers. obs.). No such association is evident in P. saci. An al- with reasonable accuracy. Segregation is not complete ternative hypothesis of juvenile specialization is possible. however, and occasionally they were captured together The longest filament, corresponding to 36% SL, is seen in the same net (F. Dagosta, pers. obs.). The abdomen is in the smallest specimen. In the second specimen, only distended with blood in several specimens. Some female slightly larger, the filament is reduced to 26% SL. Other specimens (two each in MZUSP 125622 and 125626) specimens similar in size to the latter show no sign of fil- have large eggs, approximately eye-sized or slightly larg- ament. So, if the filament is indeed a juvenile specializa- er, visible by transparency (Fig. 2). Distribution of eggs tion, it is reduced very abruptly in the course of ontogeny extending along ventral margin of hypaxial musculature (or perhaps broken off). Resolution of this question will from shortly posterior to end of pectoral fin to nearly end have to await additional material and data. of abdominal cavity, with approximately 20 eggs visible The extremely reduced opercular and interopercular in lateral layer of each side (certainly more in inner por- armatures of Paracanthopoma saci, a reduction reflected tions of gonad). in their vestigial (opercular) or absent (interopercular) in- tegument folds, raises questions about the functionality Etymology of that complex in the species. One specimen in MZUSP 125626 is preserved with opercular odontodes erect, a The name honors the SACI expedition (South sign that the biomechanical links usually associated with American Characiform Inventory, under direction of the movement of the opercular patch of odontodes are N. Menezes) which collected the first known specimen still functional in the species. No such evidence exists for of this species. Appropriately, Saci is also the name of the still more reduced interopercular armature. Given a Brazilian rural folklore supernatural entity (complete that the latter is not only tiny in size in P. saci but also name: saci-pererê), personified as a nocturnal, one- quite buried in integument, it may be reduced to a ves- legged, hopping, red-capped, pipe-smoking black boy, tigial condition. Reductions of opercular and interoper- transmutable into dust devils and fond of mischievous cular armature are recurrent in different lineages of deeds aimed at terrorizing or annoying people and other sand-dwelling trichomycterids, such as psammophilic . taxa in Glanapteryginae and . Despite such reductions, it is certain that P. saci is hematopha- Remarks gous like all other vandelliines, because several speci- mens in MZUSP 125626 have visible coagulated blood in Paracanthopoma saci is the only species of their guts. Paracanthopoma outside of the core Amazonian drain- ages (see Geographical Distribution above) and only the Geographic distribution second species of Vandelliinae from the entire Paraná- Paraguay basin (the other being Paravandellia oxyptera). The species is so far known from a single locality in In addition to the new species of Ernstichthys reported the Upper Rio Taquari system (Rio Paraguay drainage). It below, other fish collected with P. saci were all typical marks the southernmost limit of the genus. members of the Paraná-Paraguay fish fauna, including some endemics (e.g., Cyphocharax gillii, Steindachnerina Conservation status brevipinna, Creagrutus meridionalis, Brachychalcinus ret- rospina). As a member of Paracanthopoma, P. saci is a Paracanthopoma saci is endemic to Brazil and only genus-level addition to the general composition of the known from its type-locality at the upper Rio Taquari. Paraguay basin. Its area of occupancy (AOO) (B2) 4 km² is based on this Two paratypes of Paracanthopoma saci have ex- only known record. The AOO is likely underestimated traordinarily elongated first pectoral-fin rays (part of and since its hematophagous habits may mean that its MZUSP 125626, see Description above). This is the most transported by host fish over distances beyond its own Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 9/23 vagility limits, as reported for a congener (Zuanon & (vs. i+7); by the presence of i+6 anal-fin rays (vs. viii+4); Sazima, 2005). Although the Rio Taquari has historically by the basipterygium entirely hidden in integument (vs. been reported to carry a large sediment load, this charac- anterolateral arm of basipterygium exposed on the skin, teristic has intensified starting in the late 1970’s, with the forming rugose shield). increase of agriculture and pasture in the region (Soriano et al., 2001). It has been proposed that Quartzipsamment Description soils in the region are important sources of sediments that intensify siltation of the Taquari (Galdino et al., 2013), General body aspect, shape and pigmentation in which is considered as the most serious environmental Figs. 4‑5. Morphometric data in Table 3. Dorsal and ven- and socio-economic problem in the Pantanal (Soriano tral profiles of body and head in nearly mirror images of et al., 2001). Because P. saci is hematophagous, it is nec- each other, gently convex to origins of dorsal and anal essary to better know its natural hosts. If such hosts are fins, respectively, then straight along to nearly end of migratory species, they may also be negatively impacted caudal peduncle. Greatest depth of body at posterior by siltation, thus representing a threat to the feeding re- part of head and greatest width between bases of pec- sources of P. saci. Such a situation represents a continu- toral-fin spines. Caudal peduncle depressed for most of ing decline of habitat quality. At present, none of those its length, except for compressed terminus near base factors are known in any detail and therefore we sug- of caudal fin. Caudal peduncle least deep at ca. three- gest the species is assessed as DD (iii) according to the fourths of its length. Head depressed, gently convex in International Union for Conservation of Nature (IUCN) dorsal and ventral profiles. Mid-dorsal cephalic region categories and criteria (IUCN, 2020). with three bony prominences disposed in line, anterior one occipital, at limit between supraoccipital and neu- ral complex of Weberian apparatus, second one formed Ernstichthys taquari sp. nov. by posterior part of neural complex of Weberian appa- http://zoobank.org/17ADE44D-AB3D-407A-AA08-9011EFE0F470 ratus and third one immediately anterior to dorsal fin, (Figs. 4‑6) formed by central portion of middle nuchal plate (Fig. 6). Anterior cranial fontanel large, elongate-ovoid, with an- Holotype: MZUSP 125825, 22.8 mm SL, Brazil, Mato terior portion narrower than posterior one, occupying Grosso do Sul, Alcinópolis, Rio Taquarizinho (tributary most of body of mesethmoid and anterior half of length to rio Taquari, rio Paraguay drainage) (18°12 14.8 S, of frontals. Posterior fontanel about 30% shorter and 10% ′ ″ 53°34 11.3 W), elev. 363 m, col. F. Dagosta, A. Ferreira, R. narrower (at widest portion) than anterior one (Fig. 6A), ′ ″ Zanon, 18 Sep 2019. delimited mostly by frontals and only posterior end by supraoccipital. Frontals mostly separated from each oth- Paratypes: MZUSP 125826, 2 ex, 20.2‑22.7 mm SL, col- er at midline by fontanels, contacting at a small portion lected with holotype. at their midlength, corresponding to the epiphyseal bar,

Diagnosis Table 3. Morphometric data of Ernstichthys taquari. Range, mean, and SD (standard deviation) include holotype. Ernstichthys taquari differs from all congeners by: 1) the relatively narrow bilateral bony shields on dorsal holotype n min max mean SD and ventral series, which do not overlap or contact each Standard length (mm) 20.2 3 20.2 22.8 21.9 1.5 other anywhere in both series (vs. adjacent shields con- Depth at dorsal-fin origin 24.8 3 23.3 24.8 23.9 0.8 tacting or overlapping along most or entire series; this Snout to dorsal-fin origin 30.2 3 28.7 30.2 29.4 0.8 trait also distinguishes the species from most hoplomy- Snout to pectoral-fin origin 16.8 3 16.1 16.8 16.6 0.4 Snout to pelvic-fin origin 36.5 3 35 36.5 35.5 0.8 zontine species except those of Hoplomyzon); 2) the pres- Snout to anal-fin origin 18.8 3 17.1 18.8 17.8 0.9 ence of seven or eight serrations on the posterior margin Caudal-peduncle depth 8.6 3 7.9 8.6 8.2 0.3 of the pectoral spine (vs. 10‑18); 3) the pectoral-fin spine Caudal-peduncle length 20.8 3 18.9 20.8 19.8 1.0 only slightly larger than subsequent soft rays, so that Pectoral-fin length 17.5 3 17.1 17.5 17.3 0.2 there is a gradual transition between the spine and the Pelvic-fin length 45.3 3 44.6 45.4 45.1 0.4 rest of fin (vs. spine 25% longer or more than soft rays, Pelvic-fin origin to anal-fin origin 14.5 3 14.2 14.8 14.5 0.3 leaving large portion of protruding spine without cor- Dorsal-fin length 18.8 3 18.3 19.9 19.0 0.8 responding fin web distally). Further distinguished from Dorsal-fin base length 35.1 3 34.9 35.6 35.2 0.4 E. megistus by the presence of a well-developed rictal Anal-fin length 16.8 3 15.2 16.8 15.8 0.9 barbel (vs. barbel absent or reduced to bump). Further Anal-fin base length 56.0 3 55.5 56.2 55.9 0.4 distinguished from E. intosus by the unbranched maxil- Eye to dorsal-fin origin 6.6 3 6.6 8.4 7.3 1.0 lary barbel (vs. with thread-like secondary barbels); by Dorsal-fin origin to caudal-fin base 23.4 3 22.1 23.4 22.6 0.7 the lack of dentations along the anterior margin of the Head length 32.6 3 31.3 32.6 31.9 0.7 pectoral fin (vs. dentations present); by the presence of Horizontal eye diameter 41.3 3 41.3 43.1 41.9 1.1 two pairs of stout and regularly-positioned mental bar- Snout length 9.1 3 7.6 9.1 8.2 0.8 bels (Figs. 4‑5; vs. over 100 thread-like and uniformly dis- Interorbital width 18.4 3 18.4 22 20.5 1.9 tributed barbels); by the presence of i+4 dorsal-fin rays Upper jaw length 56.9 3 56.9 62 59.4 2.5 Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 10/23

Figure 4. Ernstichthys taquari, Brazil, Mato Grosso do Sul, Alcinópolis, Rio Taquarizinho State, MZUSP 125825, holotype, 22.8 mm SL. (a) Lateral view, (b) dorsal view, (c) ventral view. Photos by V. Reis. Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 11/23 with two frontals forming H‑shaped configuration in partly covered by anteromesial flap of skin. Posterior na- dorsal view. Supratemporal fossa (not visible externally) res more widely separated from each other than anteri- roughly oval, positioned between posterior portion of or ones, by distance approximately equal to interorbital. mesial margin of pterotic and posterior portion of later- Mouth subterminal, slightly wider than interorbital, with al margin of supraoccipital (Fig. 6). Transverse process of both jaws in gentle continuous arcs, and lower jaw short- vertebra 5 slender, expanded distally and curved slightly er than upper jaw. Teeth entirely absent on both jaws. posteriorly (Fig. 6A), its distal edge exposed at surface of Upper lip well delimited laterally by tumescent maxil- integument. Eye small, located dorsally on head slightly lary barbel bases, with large irregular-shaped and posi- anteriorly to middle of HL, twice as close to midline as to tioned papillae immediately at mouth opening. Lower lateral margin of head in dorsal view (Figs. 4‑5). Eye visi- lip smooth at edge of mouth but densely large-papillate ble only partially in lateral view (Figs. 4‑5). Axillary gland further posteriorly, with papillate covering extending pore small, slit-like when collapsed, located immediate- onto mental region. Mandibles thin and delicate, lack- ly posterodorsally to base of pectoral fin. Vent located ing bony contact at symphysis. Premaxillae shaped as slightly anterior to transversal through midlength of last large elongate plates jointly forming nearly continuous pelvic-fin ray. Integument heavily covered with uncul- concave bony shield internally on upper jaw. Each pre- liferous papillae on dorsal part of head and dorsal and maxilla with large stout ascending process near midline, lateral sides of body, most prominently over area around dorsoposteriorly accomodating mesethmoid cornua. margins of neurocranium, snout, half of dorsal sur- Barbels eight: one pair maxillary, one pair rictal and two face of maxillary barbels and cheeks. Unculiferous tuber- pairs mental. Maxillary barbel large, flat and expand- cles homogeneously scattered on body, not arranged in ed basally, forming most prominent feature on head. rows or any other regular pattern. Ventral side of head Maxillary barbel doubly adnate, dorsally from proximal with papillae softer and larger than those on dorsal side two-thirds of its posterior margin to cheek and ventrally of head and rest of body. from base of rictal barbel to mental region immediately Anterior nares encircled by short tubule, longer pos- anterior to anterior mental barbel. Skin folds of adnation teriorly, and separated from each other by distance short- forming deep pocket lateral to rictus and anterior to cor- er than interorbital. Posterior nostrils larger than anterior onoid process of mandible. Rictal barbel short, directed ones, separated from eye by one orbital diameter and ventrally or ventrolaterally, inserted ventrally at anterior

Figure 5. Ernstichthys taquari, MZUSP 125826, paratypes. Left side specimen 20.2 mm SL: (a) lateral view, (b) dorsal view, (c) ventral view; right side specimen 22.7 mm SL: (d) lateral view, (e) dorsal view, (f) ventral view. Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 12/23 attachment of ventral adnation of maxillary barbel, Two ered with integument and not conspicuous on surface pairs of mental barbels inserted close to lateral margin of body. Dorsal and ventral series running alongside of ventral side of head; posterior one twice as long and mid-dorsal and mid-ventral lines, respectively. Lateral thick as anterior one. Branchiostegal membranes broad- series extending along midlateral line of each side of ly united to isthmus, without free fold. Gill openings ven- body. Dorsal series formed by 21 heavily ornamented tral, reduced to small oblique slits anteromedial to inser- shields extending from immediately anterior to dor- tions of pectoral spines, approximately twice as wide as sal fin to end of body. Four of those shields disposed width of pectoral-fin spine base. Branchiostegal rays four, alongside base of dorsal fin. First shield of dorsal series first one short and thin, attached to middle of anterior formed by greatly expanded posterior nuchal plate, ceratohyal. Remaining three branchiostegal rays longer supported by bilateral dorsal processes of vertebra and stouter than first one, attached to posterior end of 8. Remaining 20 dorsal shields formed by expanded anterior ceratohyal. tips of bilateral dorsal processes (Fig. 6) on vertebrae Pectoral fin large, I+6+i *(3), with soft branched rays 9 to compound ural centrum. Anterior fourteen verte- thin and delicate, shorter than spinous ray but not to brae-derived shields bilateral, gradually closer together same degree as in other species of Ernstichthys. Pectoral- at the midline posteriorly. Posterior six shields median, fin spine long, 35‑36% of SL, with triangular soft tissue progressively narrower posteriorly. Elements of dorsal cap distally. Anterior margin of spine smooth, without shield series not overlapping each other and not con- serrations. Posterior margin with seven large pungent tacting those of lateral series, except for last one which antrorse serrations, progressively larger distally, plus barely touches dorsal margins of penultimate and an- one or two proto-spinous bony bumps basally. Cleithral tepenultimate lateral plates. Ventral shield series with bullae large and conspicuous, forming widest part of 16 heavily ornamented bony shields, with two anterior body and head in dorsal view. Postcleithral process large, ones anterior to anal fin. First shield largest, formed by broad and abruptly narrow and pointed distally, reach- distal expansions of hemal arch of vertebra 9, broader ing to middle of Weberian centrum in lateral view, and al- anteriorly than posteriorly and with concave anterior most to vertical through tip of coracoid process. Posterior and posterior margins, its anterior margins produced coracoid process long, slightly curved mesially distally, into anterolateral processes distally approaching pos- its tip reaching half-length of basipterygium and almost terior processes of basipterygia. Second ventral bony to base of pelvic fin. Pelvic fin long and pointed, insert- shield immediately anterior to anal fin, lozenge-shaped ed well anteriorly to vertical through origin of dorsal fin, and formed by distally-expanded first anal-fin ptery- i+5*(3), with first ray thickest of series and 30% shorter giophore. Remaining 14 shields formed by distal ex- than second. Second pelvic-fin ray longest of series and pansions of bilateral ventrolateral vertebral processes, thicker than all other rays except first. Basipterygium extending to posterior-most vertebra anterior to caudal with long pointed posterior process reaching almost to centrum. Of those, nine anterior ones bilateral (six of transversal through anterior tips of first ventral shield. which disposed alongside anal-fin base) and remain- Dorsal-fin origin well anterior to half of SL, entirely ad- ing five ones median, latter clearly formed by conflu- nate posteriorly, to end of last fin ray. Dorsal spinelet (or ence of bilateral portions. Posterior five ventral shields first spine, or spine lock) absent, first ray (homologous broader than long, except for long isosceles-triangular to main dorsal-fin spine) not spinous, flexible, segment- last element. Ventral shields not overlapping each other ed and without serrations. Dorsal-fin rays I+4*(3). Four and not contacting any element of lateral series. Lateral dorsal-fin pterygiophores broad and angulate in shape, series composed of actual plates or scutes, contrary to pierced by large irregular fenestrae. Anterior nuchal plate dorsal and ventral series, and formed by modified and absent. Remaining nuchal plates described above under hypertrophied lateral-line ossicles lacking direct con- dorsal shield series (Fig. 6). Adipose fin absent. Anal fin tact with vertebral column. Lateral shields not orna- insertion at vertical through end of dorsal-fin base, partly mented and covered with thick integument, not readily adnate, to ca. two-thirds of last ray, with small free edge visible on external aspect of body. Transition of lateral at end. Anal-fin rays i+6*(3), third and fourth rays longest. line tubules into plates gradual, starting at ninth ossi- Seven anal-fin pterygiophores progressively smaller pos- cle, approximately at vertical though end of dorsal-fin teriorly, four anterior ones squarish and irregularly fenes- base, and progressively more expanded towards caudal trated, posterior three rectangular and lacking fenestrae. fin. Overlap among plates starting at ossicle 15, form- Caudal fin 5+4*(3), with lower lobe longer than upper ing complete shield on sides of body from that point one as consequence of elongate lower principal fin-rays. on. Total of 34 plates, each with central blunt knob of Profile of upper lobe straight or gently sinusoidal, that thickened bone except for last one (Fig. 6), collectively of lower lobe convex and round. All principal rays close- forming lateral serration. Knobs gradually less promi- ly set, nearly adpressed at base. Outer rays thicker and nent posteriorly, covered with thick soft skin and con- with bases much stouter than that of remaining rays. centration of papillae. Knobs centrally located on ante- Procurrent caudal-fin rays represented by single ventral rior plates but gradually displaced dorsally starting on element, spine-like and bent near base. Dorsal procur- 24th plate. Spacing between knobs slightly decreasing rent caudal-fin rays absent. towards caudal fin. Body armored with three series of bony elements: Total vertebral count 29 (including those in Weberian dorsal, ventral and lateral, all of which heavily cov- complex). Ribs absent. Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 13/23

Figure 6. High-resolution x‑ray computerized microtomography (HRXCT) of Ernstichthys taquari, MZUSP 125825, holotype, 22.8 mm SL. (a) Dorsal view, (b) lat- eral view of left side, (c) ventral view. acf: anterior cranial fontanel; ach: anterior ceratohyal; ang: anguloarticular; bp: basipterygium; br: branchiostegal rays; cl: cleithrum; co: coracoid; cv: complex vertebra; den: dentary; ds: dorsal shield element; eap: expanded first anal-fin pterygiophore (= second ventral shield); ehs: expanded hemal spine (= first ventral shield); fr: frontal; hyo: hyomandibula; io1: first infraorbital; iop: interopercle; let: lateral ethmoid; lp: lateral plate element (= expanded lateral-line ossicle); mes: mesethmoid; mnp: middle nuchal plate; mx: maxilla; op: opercle; pa: parasphenoid; pal: palatine; pch: posterior ceratohyal; pfr: pelvic-fin rays; pfs: pectoral-fin spine; pmx: premaxilla; pnp: posterior nuchal plate (= first dorsal shield); pso: parietosupraoccipital; pto: pterotic; pv5: para- pophysis of fifth vertebra; qu: quadrate; sc: posttemporosupracleithrum; spo: sphenotic; vh: ventral hypohyal; vs: ventral shield element. Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 14/23

Pigmentation in alcohol fifth. Pectoral fin with large dark field crossing distal por- tion of first soft fin ray and mid-distal adjacent portion Pattern of dark pigmentation highly variable. Four of pectoral-fin spine. Small independent dark spot over conspicuous saddles of dark coloration across dorsolat- bases of last four rays. Rest of pectoral fin with scattered eral surface of body, extending in faded version ventrally dark chromatophores. Distal portion of pectoral-fin spine and gradually smaller posteriorly. White round areas in and soft-tissue terminus abruptly white. Dorsal surface dorsal view between first, second and third dark saddles, of pelvic fins covered with irregular dark fields denser due to concave profiles of posterior margin of first saddle, than those on anal fin. Ventrally, very dark field cover- anterior and posterior profiles of second one and anterior ing basal portion of rays and region between fin bases, profile of third one. First dark saddle largest, covering en- continuous anteriorly with remainder of abdominal dark tire area between pelvic- and dorsal-fin bases, extending pigmentation. over basal half, or more, of latter. Dorsal area and shape of saddle variable. In one paratype restricted to doubly-con- Ecology cave band across most of anterior part of dorsal fin, but not to base of spine (Fig. 5E). In other paratype, band Ernstichthys taquari was collected in a white water riv- covers broad squarish area on and around anterior half er, with moderate water flow, over substrate composed of dorsal fin, extending anteriorly continuously as narrow of rock and sand. Contrary to most hoplomyzontines, its straight mid-dorsal dark band over occipital region and habitat is not the deep bottom of a large river, but rather then expanding laterally as bilateral wings over posterior a small river accessible by hand-seining. Aquatic macro- margin of neurocranium (Fig. 5B). In holotype, anterior phytes were present in some sites and riparian forest was saddle vast, covering entire dorsum and sides in continu- well preserved. All specimens were collected in a shaded ous dark area from anterior 60% of dorsal fin to posterior sector covered with dense vegetation and large rocks on third of head. Second dark saddle immediately posterior the bottom. The species was not locally abundant at the to end of dorsal fin, extending ventrally and narrowing to time of collection, with only three specimens found in end of anal-fin base, its mid-lateral part prolongued an- the course of five hours of collecting effort. teriorly and in one paratype broadly cojoining anteriorly with first saddle along midlateral line. Third dark saddle Etymology beginning approximately at posterior third of caudal peduncle. Fourth saddle smallest, covering region of The specific name taquari is a reference to the rio proximal portions of caudal-fin rays but not reaching last Taquari. The word is of Tupi language origin (takwa’ri) ventral ray. Cheeks with dark cloud extending ventral- combining ta’kwara (a common name for bamboo-like ly towards pectoral-fin base and region around base of plants of family Poaceae) plus ‘i’ for diminutive. A noun posterior mental barbel. In holotype and one paratype, in apposition. dark cheek fields continuous dorsally with striking trans- versal dark band across eyes (trans-ocular band), forming Remarks conspicuous mask-like pattern. Barbels white, except for uniform dark covering on dorsal surface of proximal half Intraspecific variation in pigmentation in Hoplomy- of maxillary-barbel base in holotype and one paratype zontinae has been well-documented in Micromyzon (Fig. 5E). Axillary gland pore white. Tubercles on dorsal akamai (Chuctaya et al., 2020) and in Hoplomyzon sexpa- and lateral surfaces of body and head lighter than sur- pilostoma (Taphorn & Marrero, 1990). The variation pat- rounding areas. Individual bony knobs along lateral-line tern described for H. sexpapilostoma is similar to that in shield series lighter than rest of adjacent integument, due E. taquari, with some individuals with a dark band across to concentration of white tubercles. Central part of abdo- the eyes (trans-ocular band) and others without it. This men almost entirely covered with extensive continuous is the same kind of variation here observed in E. taquari dark field from base of pelvic fins to mental region, in one (cf., Fig. 5). Taphorn & Marrero (1990) associated the pres- paratype with long light losenge-shaped area between ence of a differentiated trans-ocular band with females bases of posterior mental barbels. Abdominal dark field and juvenile specimens. In males, the band is reported continuous posteriorly with darker fields on and between to expand and to become undifferentiated from the bases of pelvic fins and anteriorly fading before lower lip. pigmentation of the rest of head. Another sexually-di- Area of branchial opening conspicuously lighter than morphic coloration trait observed by those authors in surrounding region. Vent light or white but finely rimmed H. sexpapilostoma is the size and intensity of the dark in dark. Bilateral elongate white fields posterolaterally to spot on the distal portion of the pectoral fin and spine. vent, converging towards midline posteriorly. Dorsal-fin Taphorn & Marrero (1990) note that the marking is larg- solid dark on anterior half or 60%, with distal portion cov- er and darker in males. In E. taquari, a single specimen ered only with scattered cromatophores over fin rays and lacking the trans-orbital dark band does not noticeably hyaline margin. Anal fin mostly white, with faint irregular differ from other specimens in the size of its pectoral fin dark fields not forming any pattern. Caudal fin with dark spot. Unfortunately, the limited number of specimens saddle described above over base of fin rays, followed by available does not allow at this time the sex verification narrow white vertical band and then faint irregular dark of individuals of E. taquari. Thus, the possible association smudges over rest of fin web, abruptly fading on its distal of such pigmentation variation with sexual dimorphism Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 15/23 remains unverified in the species. In any case, the parallel Geographic distribution of the two pigmentation patterns of E. taquari with those in H. sexpapilostoma are highly suggestive of a similar Ernstichthys taquari is so far known from the type lo- sexually-dimorphic association. cality in the rio Taquari, tributary of rio Paraguay basin An unidentified species of Ernstichthys from the Rio (Fig. 3). Araguaia was reported and illustrated by Jarduli et al. (2014) and hypothesized as sister group to clade E. an- Conservation status duzei + E. megistus (Cardoso, 2008). The photograph in Jarduli et al. (2014, p. 507) shows a fish similar to E. taquari Ernstichthys taquari is endemic to Brazil and only in dorsal and lateral views, but with some visible dif- known from its type-locality at the upper Rio Taquari. Its ferences. The strongly bent distal portion of the pecto- area of occupancy (AOO) (B2) of 4 km² is based on this ral spine of the Araguaia specimen, as well as the great only known record. The AOO is likely underestimated length discrepancy between the spine and the soft rays since representatives of the genus are very rare in collec- (a common feature in most species of Ernstichthys) are tions. As discussed above in the corresponding section not present in any of the specimens known of E. taquari. on Paracanthopoma saci, siltation of the Rio Taquari is the Also, the eyes of the Araguaia specimen are noticeably most critical environmental and socio-economic prob- smaller proportionally than those of E. taquari. Finally, lem in the Pantanal (Soriano et al., 2001). Aspredinidae the particular color pattern of the Araguaia specimen often occupy specific and rather complex microhabitats (with a thin inter-ocular bar but no trans-orbital bar and and siltation likely extirpates the type of environments more or less regular-sized small spots forming a speck- that E. taquari likely requires. A continuing decline in led covering on head and dorsum) is also not present in habitat quality b (iii) is inferred based on the still grow- any E. taquari (although not much weight attaches to this ing pasture areas and siltation. It is not possible to meet difference because of the wide pigmentation variation in subcriterion ‘a’ because the population is not necessarily species of Hoplomyzontini and the limited number of fragmented. Therefore, we suggest this species is clas- specimens available). It is impossible at this time to con- sified as Near Threatened, close to meeting Critically fidently resolve the taxonomic status of the Ernstichthys Endangered (CR) by the following criteria B2b (iii) accord- specimen from the Rio Araguaia illustrated in Jarduli ing to the International Union for Conservation of Nature et al. (2014). Preliminary differences noted above, how- (IUCN) categories and criteria (IUCN, 2020). ever, suggest that it is not conspecific with E. taquari. Another report of Ernstichthys in the Brazilian Amazon is provided in Ohara & Zuanon (2013) on the basis of DISCUSSION a single specimen from the Rio Madeira, identified as E. cf. anduzei. As noted by the authors (p. 125), this par- The phylogenetic placement of Paracanthopoma saci ticular specimen does not conform to E. anduzei in the in Vandelliinae is supported by all synapomorphies so far number of dentations in the pectoral-fin spine (nine; vs. proposed for the subfamily, a very strongly-corroborat- 10 to 14). Also, the gentle curvature of the pectoral-fin ed monophyletic group. Those include the dentaries not spine and the relatively gradual length difference be- meeting at the midline; the presence of “claw-like” teeth tween the spine and soft rays both do not match the in the premaxillae; the lack of the fifth ceratobranchial rather abrupt distal spine curvature and the large length and associated toothplate; the absence of hypobranchi- discrepancy between spine and soft rays in E. anduzei. als two and three; the toothless upper pharyngeal tooth- In both traits, the Madeira specimen approaches condi- plate; the absence of vomer; the absence of mesocora- tions in E. taquari, an obviously more similar taxon. Like coid; and the fully cartilaginous fourth pharyngobranchi- in the preceding case, some differences exist that are in- al (Baskin, 1973; de Pinna, 1998; DoNascimiento, 2012) dicative that the two are not conspecific. First, the pale plus some unique myological synapomorphies (Datovo coloration of the Madeira specimen lacks most dark pig- & Bockmann, 2010). Finally, the specialized feeding on mentation typical of hoplomyzontine species other than the blood of other vertebrates, given its uniqueness, is those of Micromyzon. Barring some post mortem bleach- also valid evidence for monophyly, although one which ing of the specimen, this is well beyond the intraspecific at this point refers to general biology rather than specific variation expected in the group. Second, its number of character states. pectoral-fin spine dentations (nine) is intermediate be- Paracanthopoma is perhaps the most clearly-defined tween E. taquari (7‑8) and E. anduzei (10‑15). Finally, the genus in Vandelliinae. The integument fold across the pectoral-spine length of that specimen is 31.8% SL (mea- isthmus is an easily-observable character that occurs sured from the published photograph), thus significantly nowhere else in Vandelliines and has been part of the shorter than that of E. taquari (35‑36.5% SL). The summa- diagnosis of the genus since its establishment (Giltay, tion of those differences suggests that the specimen of 1935). It is also a unique feature among its closest rela- E. cf. anduzei reported in Ohara & Zuanon (2013) is not a tives, the and Tridentinae. Although nearly representative of E. taquari. As before, however, such ev- all tridentines (except Miuroglanis) and some stegophil- idence is insufficient to properly resolve the question at ines (Acanthopoma, Apomatoceros and Schultzichthys) this time. More material and direct comparisons of spec- have superficially similar structures, they all differ from imens are needed. the situation in Paracanthopoma. The membranes in Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 16/23

Tridentinae are actually free branchial membranes, with for subsets of the genus (a discussion of this topic, in the completely embedded branchiostegal rays and not at- context of P. parva and one of the undescribed species, tached to the isthmus (or only narrowly attached ante- is provided in DoNascimiento, 2012). Regardless of such riorly), leaving a large unconstricted branchial opening. factors, little doubt exists that P. saci is the closest relative In stegophiline taxa mentioned above, the membrane is of P. parva among currently-known vandelliine diversity. broadly attached to the isthmus (a condition general in Species-level distinction between P. saci and P. par- the clade consisting of Stegophilinae and Vandelliinae, va is well-corroborated by a series of conspicuous dif- none of which has free branchiostegal membranes) and ferences in various body systems, as summarized in the the free flap is clearly a portion of the membrane poste- Diagnosis above. The distinctions are pronounced in kind rior to the fusion, because it contains embedded bran- and degree, resulting in fishes with very different general chiostegal rays. The situation is easily verified in alcoholic aspect and which can be distinguished at a glance with or c&s material by lifting the membrane and observing the naked eye, despite their small size. Examination of the totally included set of rays in the free flap. The struc- series of P. parva (cf., Comparative Material) plus 15 spec- ture is very different in Paracanthopoma. Here, the free imens of P. saci demonstrate that none of those diag- fold does not consist of a free branchiostegal membrane, nostic characteristics is subject to intraspecific variation contrary to reported in the original description of the sufficient to bridge the gaps between the two species. genus (Giltay, 1935) and repeated in several subsequent In fact, the profound differences in body and head struc- publications and keys. The actual branchiostegal mem- ture suggest species with quite different biologies. The brane in Paracanthopoma is nearly entirely fused to the delicate mouth dentition of P. saci is probably associated isthmus, leaving the branchial opening reduced to a with a specialization on smaller hosts and perhaps subtle small passage limited to the region between the opercu- approaching strategies, when compared with the brut- lar and interopercular patches of odontodes, as in all oth- ish oral armature of P. parva. Also, the spatulate caudal er vandelliines. The integument fold across the isthmus peduncle is indicative of a swimming mode based on in Paracanthopoma is actually an independent structure propelling by the posterior part of the body, rather than that overlays the whole isthmal region. It contains no by undulations of the entire body. All those factors in- branchiostegal rays, which are located entirely in the soft dicate that considerable divergence exists between the tissue anterior to the fusion with the isthmus. The fold two species of Paracanthopoma. In fact, species diversity forms a broad and deep integument flounce extending of the genus is substantially larger than presently docu- continuously across the isthmus, with no embedded mented not only in species numbers but also in pheno- rays. The Paracanthopoma fold is probably a derivative typic divergence, as an ongoing revision of the group by of the branchiostegal membrane, but constitutes a set the authors confirms. of specialization exclusive to the genus. In order to high- Hoplomyzontinae is a strongly-supported mono- light its neomorphic nature and avoid further confusion phyletic group. Its corroborating synapomorphies with the branchiostegal membrane itself, here we call it are not only numerous and diverse, but they are also a branchiostegal velum. highly conspicuous. Their body armor, for example, is Comparative examination of the anatomy of unique among aspredinids. Although some other cat- Paracanthopoma reveals other putative synapomorphies fish groups also have a body armor, such as distal lori- for the genus in the skeleton. For example, species of the carioids (Callichthyidae, Scoloplacidae, and Loricariidae), genus (including all new taxa known to us) have a dis- , Amphiliidae (Doumeinae), and Sisoridae tally bifurcated maxilla, a unique configuration among (Sisor), structural details of the armor in hoplomyzon- the otherwise single-headed maxillas of other vandel- tines are unique. They are the only mailed liines and trichomycterids in general. Their median pre- where the bony shielding is formed by a combination maxilla is also different from that of all other vandelliines of emerging vertebral expansions (dorsal and ven- and stegophilines (the only taxa having that structure) tral shield series) and independent plates formed from in having bilateral dorsal flanges bracing the neck of the modified lateral-line ossicles in the lateral series (Friel & mesethmoid immediately posterior to the mesethmoid Lundberg, 1996). Other undisputed synapomorphies for cornua. The median premaxilla in other taxa lacks an the subfamily include the absence of ribs, absence of elaborate dorsal surface of that bone (a non-homolo- urohyal, 5+4 principal caudal-fin rays, premaxilla with an gous median process is present in most stegophilines). anterior limb, the anterior displacement of the pelvic fin A complete phylogenetic evaluation of Paracanthopoma and girdle so that the basipterygia lie very close to the lies beyond the scope of the present paper, but a hypoth- coracoids, partly included between coracoid processes esis of its monophyly is well-supported by a few unique, (Friel, 1994). Ernstichthys taquari shares all those synapo- uncontradicted and well-defined character conditions morphies and little doubt remains as to its placement in (in addition to the characters above, an additional list Hoplomyzontinae. is provided in DoNascimiento, 2012, not explicitly enu- The generic allocation of the new species needs merated here because that work is still unpublished). Of more detailed discussion because the relevant set of course, not all unique characteristics shared between evidence is less decisive than that for the subfamily lev- P. saci and P. parva will necessarily be synapomorphic for el. The long pectoral-fin spine is the most visible simi- the entire genus once its species diversity is more com- larity that E. taquari shares with other species currently pletely mapped, because some will be synapomorphic in Ernstichthys. This is clearly an apomorphic condi- Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 17/23 tion. Other hoplomyzontines allocated in Hoplomyzon, such caveats, some information from the preanal shields Micromyzon, and Dupouyichthys have a proportionately is certainly useful taxonomically and, if properly studied, much shorter spine, similar in that regard to that in oth- helps to further test the generic affinities of E. taquari. er aspredinids and catfishes in general. Although the The anteriormost preanal shield is a median vertebral pectoral-fin spine in E. taquari is more similar to that of derivative formed from a distally expanded hemal spine congeners than to that of other genera in the subfam- (see Description above). In E. taquari, that shield is as ily, it is also noticeable that its condition is the least ex- long as broad or slightly longer than broad, has long di- treme in the genus. Other species of Ernstichthys have verging arms anteriorly (around the anal and urogenital a comparatively longer and more distally curved spine, openings area) and its anterior and posterior margins are approximately twice as long as the rest of the fin. Also, in strongly concave. This is the same overall shape seen in E. taquari the size discrepancy between the pectoral-fin E. anduzei and E. megistus, but not in E. intonsus, where it spine and remaining fin rays is not as dramatic (Figs. 4‑5). is arc-shaped, much broader than long, concave anteri- Thus, the situation of the pectoral fin in E. taquari is inter- orly and convex posteriorly (cf., Stewart, 1985: figs. 1D‑F; mediate between the state in other Ernstichthys, on the Taphorn & Marrero, 1990: fig. 3C). Although not present one hand, and the one in remaining hoplomyzontines, in all species currently in Ernstichthys, the peculiar shape on the other. Friel (1994) lists as an unambiguous synapo- of the first preanal shield is not present in any other hop- morphy for Ernstichthys an expanded and distally-flared lomyzontine, thus constituting valid evidence of rela- transverse process of the fifth vertebra, different from the tionships. The second (middle) shield, also a hemal spine thin and evenly wide process of other hoplomyzontines. derivative, is long and narrow in E. taquari, E. megistus Ernstichthys taquari clearly shares the distally expanded and E. intonsus, but in E. anduzei it is variable, either long transverse process of the fifth vertebra (Fig. 6A). as in congeners or roundish (Stewart, 1985: 15). The mid- A few other characteristics are corroborative of that dle preanal shield is also somewhat elongate in M. aka- allocation, although they must be considered as provi- mai (Friel & Lundberg, 1996: fig. 4) but not to the same sional at this point because relevant comparative infor- degree as in species of Ernstichthys listed above. mation is not available for all hoplomyzontine species. The dorsal and ventral bony shield series in all spec- For example, the shape of the coracoid process, broad imens known of Ernstichthys taquari differ from those of for most of its length and then pointed at the tip, is very all congeners in being comparatively narrow, thus failing similar in E. taquari and other Ernstichthys species (cf., to overlap or contact each other along most of the two Taphorn & Marrero, 1990: fig. 2C) and different from the series except the posterior, medially-united elements. In blunt, medially-curved shorter process in other hoplo- most other hoplomyzontines, the plates contact or even myzontine genera (cf., Taphorn & Marrero, 1990: fig. 2A; broadly overlap their neighbors. This trait in fact differen- Carvalho et al., 2016: fig. 4A; Carvalho et al., 2017: fig. 4A). tiates E. taquari from all other hoplomyzontines except It also deserves notice that the structure of the basipte- species of Hoplomyzon, which also have narrow, non-con- rygium in E. taquari is very similar to those of at least tacting dorsal and ventral shields. However, details of the some other congeneric species, with a broadly-triangular shape of the plates differ in E. taquari and Hoplomyzon anterior arm directed straight towards the posterior sur- species. In Hoplomyzon, the shields are roundish and face of the coracoid (cf., Taphorn & Marrero, 1990: fig. 2C). symmetrical in shape (Carvalho et al., 2017). In E. taquari, This is different from the condition in hoplomyzontines contrastingly, the respective plates are roughly triangu- allocated in other genera, where the anterior arm of the lar and slanted posteriorly. This detail approaches the basipterygium is very short and poorly differentiated condition in E. taquari to that in its congeners, regardless from the rest of the bone, or narrow and directed antero- of the discrepant non-overlapping condition. In fact, the laterally (cf., Taphorn & Marrero, 1990: fig. 2A; Carvalho situation of the dorsal and ventral shields in the species et al., 2016: fig. 10, 2017: fig. 10). seems like an attenuated form of that in other species of Much weight has been given to so-called preanal Ernstichthys. bony “plates” (actually not always true plates, see above) Ernstichthys taquari also shares characters states at in hoplomyzontine taxonomy, which are serially posi- more inclusive clades within hoplomyzontines that in- tioned, medially and bilaterally, anterior to and along- clude the hypothesized closest relatives of its genus. side the base of the anal fin. Those shield series are in fact For example, the species lacks premaxillary and den- morphologically heterogeneous, some shields formed tary teeth, like Dupouyichthys, Micromyzon, and other by expanded median vertebral processes or hemal Ernstichthys. The significance of this trait, however, is not spines, others by lateral vertebral processes, and finally as decisive as it once was, because Hoplomyzon cardosoi some from anal-fin pterygiophores. It has been noted also lacks teeth on both bones (Carvalho et al., 2017). that much intraspecific variation exists in the morphol- Naturally, a decision about the generic allocation of ogy of those shields (Friel & Lundberg, 1996: 647) and Ernstichthys taquari depends not only on positive evi- much of that variation remains uncharted. A majority of dence for its alignment with Ernstichthys, as done above, the shields are just the endpoints of much larger internal but also on the lack of evidence for alternative place- structures that reach the surface of the integument. Part ments. Accordingly, the species was investigated as to of the observed variation, both intra- and inter-taxonom- the presence of diagnostic characters so far proposed ically, is a result of whether or not, and to what degree, for other hoplomyzontine genera. Hoplomyzon has the terminal structures emerge at the surface. Despite been diagnosed by many characteristics in various pub- Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 18/23 lications, however a recent reevaluation (Carvalho et al., mainly in basins draining the Andean region. In addition 2017: 12‑13) concluded that a single characteristic is ac- to the examples by Dagosta & de Pinna (2019), other tually apomorphic and confirmed in all species of the ge- corroborative taxa include Gephyrocharax (Ferreira et al., nus: the presence of large well-defined papillae disposed 2018), Brycon hilarii and B. whitei (Lima, 2017) and the along the margin of the upper jaw. This is a trait which siluriforms Lamontichthys (Paixão & Toledo-Piza, 2009), has been traditionally used to diagnose the genus since Otocinclus huaorani (Schaefer, 1997), O. vittatus (Schaefer, its description (Myers, 1942) and which is not present in 1997), Pimelodella howesi (Slobodian, 2017), and Rhamdia any species of Ernstichthys, including E. taquari. poeyi (Silfvergrip, 1996). The Cis-Andean Foothills distri- The genus Dupouyichthys, with its single species, bution pattern forms an arc with the concavity directed D. sapito, is the least known hoplomyzontine genus. towards the Amazonas-Orinoco (Dagosta & de Pinna, The configuration of the preanal plates in D. sapito was 2019: fig. 21a). The extension of the arc varies among considered as synapomorphic for the genus by Stewart taxa, mainly in its southern and eastern reaches. Some of (1985) while Friel (1994) considered the presence of a those groups have a presence also in the Paraná-Paraguay single such pair as equally diagnostic. To that it might (e.g., Astyanacinus spp. – here considered as a valid ge- be added that the club-shape and orientation of the nus – Brycon hilarii, Gephyrocharax spp., Leporinus stria- bilateral shields on each side of the first (median) pre- tus, Rhyacoglanis spp.), or Tocantins (Lamontichthys spp., anal plate (Stewart, 1985: fig. 1C) are also unique among Rhamdia poeyi, Xyliphius spp.), although most examples hoplomyzontines. The same probably also holds for the have their southern limit in tributaries of the rio Madeira. rough lozenge shape of the first and second preanal As hypothesized by Vari (1988), it is likely that species shields in the species (with reservations about possible with that pattern of distribution are limited by ecolog- yet unmapped intraspecific variation). In any event, none ical requirements associated with swiftly flowing rivers. of those particularities typical of Dupouyichthys are pres- Indeed, species of Ernstichthys have been included in the ent in E. taquari. The fourth and final hoplomyzontine guild of rheophilic fishes by Lujan & Conway (2015). The genus, Micromyzon, has recently been phylogenetically type locality of Ernstichthys taquari is also the source of rediagnosed in Carvalho et al. (2016) by the following the first record of the genus Paracanthopoma (Fig. 3; re- traits: eyes absent; lateral margin of frontal straight, not cords for the genus from material directly examined for forming an orbital concavity; posterior cranial fontanel this study plus data on undescribed species from an on- reduced or absent; premaxilla absent or extremely re- going revision of Vandelliinae by the authors) outside of duced; limb of autopalatine posterior to lateral ethmoid the Amazonas-Orinoco axis. Ernstichthys clearly has a Cis- articulation about one fourth the length of anterior limb; Andean Foothills distribution associated with highlands. rows of large tubercles absent along posterior lateral Contrastingly, Paracanthopoma is a lineage broadly dis- line; dark integumentary pigmentation reduced or ab- tributed in the Amazonas-Orinoco, with both highland sent. Except for the orbital concavity character, which and lowland species (most yet undescribed). is present (albeit reduced) in the specimen examined Though exceptional, the presence of those two typ- of M. akamai, all other characters are consistent with ically Amazonian lineages (Fig. 3) in a tributary of the the observations made in association with this paper. Pantanal Wetland is not unique. It has been known for As before, E. taquari lacks each and all of those putative a long time that the headwaters of the Rio Paraguay Micromyzon synapomorphies. In sum, E. taquari does not include some odd Amazonian components, usually re- bear any convincing character evidence for its inclusion stricted in distribution (Lima et al., 2007; Ribeiro et al., either in Hoplomyzon, Dupouyichthys or Micromyzon. 2013; Lopes et al., 2020). The ecological barrier represent- Therefore, the anatomy of E. taquari not only provides ed by the Pantanal Wetland prevented such upper-wa- evidence that is the closest relative of species currently ter course, clear water, high-energy, components from allocated in Ernstichthys, but also reveals no evidence for spreading to the rest of the basin, thus explaining their alternative generic placements. narrow endemism. The presence of Ernstichthys taquari and Paracanthopoma saci are eloquent additional ele- ments in that pattern. Biogeographic framework The lack of a phylogenetic hypothesis for species of Ernstichthys and Paracanthopoma (as mentioned above, Ernstichthys taquari is the first Hoplomyzontinae spe- there are several undescribed species in the genus) cies reported for the southern half of South America. The is not a full impediment in understanding the gener- subfamily is otherwise a typical component of northern al features of their associated biogeographic history. basins of the continent, with nearly its entire diversity Important parts of that history can be inferred from in the Amazonas-Orinoco (Fig. 3). The presence of the ancestral biogeographic reconstructions based on the genus Ernstichthys in the rio Paraguay basin and in the phylogenetic position of the genera in their respective rio Araguaia basin (Jarduli et al., 2014), is congruent with families. The two genera are exclusively Amazonian, al- the pattern proposed for the group in Dagosta & de though their sister genera are not: Parandellia in the Pinna (2019). In that paper, Ernstichthys was one of the case of Paracanthopoma and Dupouyichthys in that of examples corroborating the pattern called “Cis-Andean Ernsticthys. Foothills”, composed of taxa with distributions restricted Ancestral biogeographic reconstruction from the to the uplands of the western region of South America, BBM model (Fig. 7A, D) indicates that the two new spe- Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 19/23 cies likely arrived secondarily in the Paraguay basin from taquari is in the rio Paraguay basin by geodispersal, com- the Amazonas-Orinoco-Guiana. Model S‑DIVA on the ing from the Amazonas-Orinoco-Guiana and 50% that other hand, results in a 50% probability that Ernsticthys its presence there is the result of vicariance (Fig. 7B).

Figure 7. Ancestral geographic reconstruction from Aspredinidae using BBM (7A) and S‑DIVA (7B) and from the MTSVG clade of Trichomycteridae using S‑DIVA (7C) and BBM (7D). Biogeographical regions: A = Amazon-core; B = São Francisco and Eastern Coastal drainages; C = Paraná-Paraguay; D = Trans-Andean. Black arrows indicate biotic dispersal from Amazon-core to Paraná-Paraguay region. See Materials and Methods section for further analytic details. Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 20/23

Resolution of that uncertainty must await resolution of date for potential faunal exchange with the Taquari ba- the phylogenetic position of the species among other sin. The physical proximity between the headwaters of species of Ernstichthys. In the case of Paracanthopoma the rio Taquari with its neighboring Amazonian basins is saci, S‑DIVA infers that its presence in the Paraguay re- extreme (Fig. 8), in some cases only a few hundred me- sults from vicariance, on the occasion of its separation ters. It is intuitively obvious that headwater stream cap- from the Amazonas-Orinoco-Guiana (Fig. 7C). Because ture resulted in the presence of Amazonian elements in several species of Paracanthopoma await description the upper rio Taquari. Such events are often associated (MdP, pers. obs.) all of which from the Amazonas-Orinoco- with the upper reaches of adjacent basins and is largely Guiana region, this biogeographic scenario will be tested responsible for the historically reticulate nature of riv- once more taxa are included in the analysis. Again, the er drainages (Lima & Ribeiro, 2011; Ribeiro et al., 2013; phylogenetic position of P. saci in its genus is key to a res- Dagosta & de Pinna, 2017) (Fig. 8). olution of the question. The region where both Ernstichthys taquari and Despite some degree of uncertainty, a majority of Paracanthopoma saci were collected in the upper rio resolutions support the hypothesis that both Ernsticthys Taquari is located close to the Trans-brazilian lineament, taquari and Paracanthopoma saci reached the Paraguay a major geological suture zone where Precambrian faults secondarily, from Amazonian ancestors. Although an op- have been reactivated during the Paleozoic, Mesozoic, posite scenario is theoretically possible (i.e., that those and Cenozoic (Paranhos-Filho et al., 2013). Such reac- genera arose in the Paraguay and subsequently colo- tivations are known to have caused the formation of nized the Amazon), such hypothesis requires multiple the Pantanal (Assine & Soares, 2004), with wide-scale cases of lineage extinction in the Paraguay and is not hydrological reorganization and rampant headwater supported by any of the results. The unlikeliness of such capture events in adjacent uplands (Ribeiro et al., 2013). idea is compounded by the fact that the Paraguay is by Topography shown in Fig. 3 clearly shows that the up- no means a depauperate basin in terms of fish species per rio Taquari is located at the border of the Pantanal and lineages (Fig. 7). Wetland depression and the presence of Ernstichthys The occurrence of both Ernstichthys and taquari and Paracanthopoma saci are possible additional Paracanthopoma exclusively in the upper rio Taquari may elements in that pattern. suggest a biogeographical history separate from other tributaries of the Paraguay system, even if the acquisi- tion of these Amazonian components is not necessarily Conservation of a highly endemic, poorly related with a single biogeographical event (i.e., they are known and threatened region not necessarily biographically homologous). The Taquari river basin is therefore a hybrid biogeographical unit, The two new species herein described are from the rio with part of its ichthyofaunistic composition related to Taquari, a river which is part of the Pantanal Wetland sys- the Paraguay river basin, of which it is currently tribu- tem but which drains an area of Cerrado biome where the tary, and part associated to past connections with the species were collected. The locality is part of the region Amazon. delimited and named by Dagosta et al. (2020) as “Upper Both Ernstichthys and Paracanthopoma are absent in Araguaia”. The region corresponds to the uppermost part neighboring tributaries of the rio Paraguay and upper rio of the rio Araguaia drainage, upstream of various water- Paraná, but present in the rio Araguaia, an Amazonian falls and rapids such as the falls of Couto Magalhães at tributary. This places the latter basin as a prime candi- Santa Rita do Araguaia (State of Goiás). Despite its name, the “Upper Araguaia” bioregion includes also headwaters of tributaries of the Paraguay basin, as the rio Correntes and the rio Taquari, which drain the eastern limit of the Pantanal Wetland. In addition to the two species herein reported, a num- ber of other fish endemics occur in the Upper Araguaia bioregion, such as Astyanax joaovitori, Characidium chicoi, Cyphocharax boiadeiro, Eigenmannia correntes, Hyphessobrycon eilyos, H. langeanii, H. weitzmanorum, Aspidoras velites, A. taurus, Cnesterodon septentrionalis, Melanorivulus litteratus, M. urbirajarai, Simpsonichthys cholopteryx and other three species of yet undescribed (F. Dagosta, pers. comm.). This density of en- demics is the main factor accounting for the delimitation of that area as a biogeographically distinct unit in the an- Figure 8. Water divide between upper Paraguay (black rivers), upper Paraná alytical estimates implemented by Dagosta et al. (2020). (blue rivers), and upper Araguaia (white rivers). Gray dash-line represents In fact, it is one of the smallest fish bioregions recog- the Trans-brazilian lineament. Thin yellow dashed line means water divide nized in South America. Besides its small area and abun- boundaries between neighbouring basins. Black star shows type locality of dance of endemics, the Upper Araguaia bioregion was Ernstichthys taquari and Paracanthopoma saci. highlighted by the authors as an Endemic Amazonian Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay Pap. Avulsos Zool., 2021; v.61: e20216147 21/23

Fish Area (EAFA) with priority for conservation. That Amazonas drainage), col. B.M. Burr et al., 09 Aug 1996. qualification is based on the scarcity of protected areas Tridentopsis cahuali, MNHNP 1448, 12 ex, Paraguay, in the region, the presence of threatened species (e.g., Presidente Hayes, Pozo Colorado, col., O. Romero et al., 20 Melanorivulus litteratus and M. urirajarai), and – mainly Apr 1996. Tridentopsis pearsoni, CAS 56200, 3 ex, Bolivia, – deforestation pressure and dam construction. The two Beni, Lake Rogoagua, col. N.E. Pearson. latter threats are particularly severe in hydrographic ba- sins draining the Cerrado biome, were a major portion of Trichomycteridae, Vandelliinae: Paracanthopoma par- the agribusiness output and electricity generation is lo- va. Brazil: IRSNB 10121, 2 ex, holotype and paratype, cated in Brazil (Latrubesse et al., 2019). The region where Brazil, upper Rio Catrimani (Rio Branco drainage), col. C. Paracanthopoma saci and Ernstichthys taquari were col- Lako; CAS 118205, 1 ex, Amazonas, upper Rio Catrimani lected has large-scale cattle farming as the main econom- (Rio Branco drainage), col. S. Lako; INPA 16555, 2 ex ic activity. On the other hand, the “Amazonian” portion of (1 c&s), Roraima, Boa Vista, Maracá, Rio Branco, col. O. the “Upper Araguaia” bioregion has a predominance of Bitar, May 1988; MZUSP 30400, 10 ex (3 c&s), Rondônia, large monocultures such as cotton and sugar cane. The Independência, main channel of Rio Machado (Rio entire bioregion is dotted with planned small hydroelec- Madeira drainage), col. M. Goulding, 06 May 1978; MZUSP tric dams, some of which already in place. Therefore, mul- 29793, 2 ex, Amazonas, Rio Negro at Cachoeira de São tiple factors demonstrate the Upper Araguaia bioregion Gabriel, col. M. Goulding, 18 May 1979; MZUSP 63076, is in imminent danger of major biodiversity loss and ur- 25 ex (4 c&s), Mato Grosso, Nova Mutum, Rio Arinos gently requires conservation measures. (Rio Tapajós drainage), col. H.F. Mendes, 16 Jan 1998; Finally, it is remarkable that the rio Paraguay basin is MZUSP 40585, 29 ex (5 c&s), Goiás, Monte Alegre de considered as a relatively well-sampled system, with a Goiás, Rio Paraná above the mouth of Rio Bezerra (Rio well-known fish fauna. The discovery of such conspicu- Tocantins drainage), col. J.C. de Oliveira & W.J.E.M. da ous elements as the new species herein reported demon- Costa, 10 Jan 1989; MZUSP 74624, 13 ex, Mato Grosso, strates that fish biodiversity in the Paraguay drainage Rio Xingu, Parque Indígena do Xingu, Posto Diauarum, and in central Brazil is still underestimated. col. G.R. Kloss, 08 Dec 1973. Ecuador: FMNH 99519, 2 ex, Río Aguarico, near Destacamento Militar Cuyabeno and confluence of Río Cuyabeno and Río Aguarico Comparative material (Río Napo drainage), col. D. Stewart et al., 21 Oct 1983. : ANSP 179207, 2 ex, Rupununi (Region 9), Ireng Hoplomyzontinae: Micromyzon akamai, MZUSP 48550, River, 6.9 km WSW of village of Karasabai (04°01 10 N ′ ″ 1 ex, holotype, Brazil, Pará, Rio Tocantins, above con- 59°36 06 W), col. M.H. Sabaj et al., 01 Nov 2002. Peru: ′ ″ fluence with Rio Pará (01°50 S, 49°17 W), col. A. Akama MUSM 4562, 3 ex Madre de Dios, Parque Nacional Manu, ′ ′ et al., 20 Nov 1994; MZUSP 48551, 3 ex, paratypes, col- Manu, Pakitza, Río Manu, col. H. Ortega, 22 Jun 1993. lected with holotype; MZUSP 48552, 1 ex, paratype, c&s, Paravandellia oxyptera. MZUSP 9597, 1 ex, Brazil, Brazil, Pará, Rio Amazonas, south side of river, across Amazonas, Anamã, Rio Solimões, col. EPA, 21 Sep 1968; from Monte Alegre, ca. 52 km downriver from mouth of MZUSP 23352, 1 ex, Brazil, Amazonas, Rio Solimões, in Rio Tapajós (02°01 S, 54°05 W), col. A. Akama, A. Zanata, front of Jacaré, near Fonte Boa, col. EPA, 07 Oct 1968; ′ ′ 04 Nov 1994. Ernstichthys sp. MZUSP 37814, 7 ex (1 c&s), MZUSP 83703, 8 ex (2 c&s), São Paulo, São Carlos, Ribeirão Brazil, Mato Grosso, Igarapé Ingazeiro, 20 km upstream das Araras (Rio Grande drainage), col. J.L. Birindelli et al., from mouth of Rio Canumã on Rio Ariuanã, below 09 Oct 2002; MZUSP 89973, 1 ex, Mato Grosso, Tangará da Dardanelos (Rio Madeira basin) (09°58 S, 59°19 W), col. Serra, Rio Sepotuba, below Salto das Nuvens (14°37 15 S, ′ ′ ′ ″ Joint MZUSP/INPA expedition, 17 Nov 1976; MZUSP 57°44 20 W), col. H.A. Britski et al., 09 Mar 2002; MZUSP ′ ″ 74184, 1 ex, Brazil, Amazonas, Rio Madeira, col. A. Zanata 90600, 2 ex, Mato Grosso, Cáceres, Rio Sepotuba (middle et al. Hoplomyzon sexpapilostoma, MZUSP 38894, 5 ex, course) (Rio Paraguai drainage) (15°24 37 S, 57°42 20 W), ′ ″ ′ ″ paratypes, , Barinas, Río Masparro, col. D. col. H.A. Britski et al., 04 Mar 2002; MZUSP 106061, 6 ex, Taphorn, C. Lilyestrom, 13 Nov 1983. Amazonas, Río Mavaca (Río Orinoco drainage), beach up- stream from base-camp of Tapirapecó Expedition, col., R. Trichomycteridae, Stegophilinae (all from Brazil): Royero et al., 22 Mar 1988. Acanthopoma annectens, MZUSP 55706, 2 ex, Amazonas, Rio Solimões, col. J. Lundberg et al., 12 Nov 1993. Apomatoceros alleni, INPA 16695, 1 ex, Amazonas, Rio ACKNOWLEDGMENTS Solimões, Costa da Terra Nova, Lago Castanho, col. M. de Pinna and L. Py-Daniel, 19 Mar 2001. Schultzichthys bondi, We thank Alexandre Ribeiro who provided valu- FMNH 105572, 31 ex, Ecuador, Rio Napo at Coca, col., D. able suggestions during development of this paper. Stewart and M. Ibarra, 01 Oct 1981. The manuscript benefitted greatly from reviews by C. DoNascimiento and T. Carvalho. We are grateful to Trichomycteridae, Tridentinae: Miuroglanis platycepha- Anderson Ferreira, Manoela Marinho, Osvaldo Oyakawa, lus, MZUSP 7805, 3 ex (1 c&s), Brazil, Amazonas, Parintins, Priscila Camelier, and Ricardon Zanon for their help in col. Expedição Permanente da Amazônia. Tridens mela- fieldwork. F.C.P.D. thanks Anderson Ferreira, Fabiano nops, INHS 40467, 3 ex, Peru, Loreto, Río Nanay (Río Antunes, Márcia Regina Russo and Adnara Ribeiro Pap. Avulsos Zool., 2021; v.61: e20216147 Dagosta, F.C.P. & de Pinna, M.: Description of two new catfish species of typically Amazonian lineages in the upper Paraguay 22/23

Gomide for administrative support at UFGD, MS and Carvalho, T.P.; Reis, R.E. & Friel, J.P. 2017. A new species of Hoplomyzon Bruna Barbosa (Prefeitura de Alcinópolis), Erciliomar (Siluriformes: Aspredinidae) from Maracaibo Basin, Venezuela: Osteological Furquim Rocha (Prefeitura de Alcinópolis) and Sandro description using high-resolution computed microtomography of a Menezes Silva (UFGD, MS) for logistical support in the miniature species. Neotropical Ichthyology, 15(1): 1‑16. DOI field. We thank V. Reis and C. DoNascimiento for many Chuctaya, J.; Encalada, A.C.; Barragán, K.S.; Torres, M.L.; Rojas, K.E; Ochoa- discussions on trichomycterid evolution and systemat- Herrera, V. & Carvalho, T.P. 2020. New Ecuadorian records of the eyeless ics. V. Reis also made photographs used in figs. 1 and 4. banjo catfish Micromyzon akamai (Siluriformes: Aspredinidae) expand Authors are partially funded for field activities to collect the species range and reveal intraspecific morphological variation. fish specimens by the Fundação de Amparo à Pesquisa Journal of Fish Biology, Short communication. DOI do Estado de São Paulo – FAPESP, http://www.fapesp. Dagosta, F.C.P. 2021. Ernstichthys ctscan Siluriformes Aspredinidae. br (F.C.P.D. #2016/19075‑9; M.P. #2015/26804‑4) and by Harvard Dataverse Online repository. [dataset]. Available: http://doi. the Conselho Nacional de Desenvolvimento Científico org/10.7910/DVN/XCXEM8. Access: 11/04/2021. e Tecnológico – CNPq, http://www.cnpq.br (F.C.P.D. Dagosta, F.C.P. & de Pinna, M. 2017. Biogeography of Amazonian fishes: #405643/2018‑7; M.P. #310688/2019‑1). deconstructing river basins as biogeographic units. Neotropical Ichthyology, 15(3): 1‑24. DOI Dagosta, F.C.P. & de Pinna, M. 2018. A history of the biogeography of AUTHORS’ CONTRIBUTIONS Amazonian fishes. Neotropical Ichthyology, 16(3): 1‑19. DOI Dagosta, F.C.P. & de Pinna, M. 2019. The fishes of the Amazon: distribution F.C.P.D., M.P.: Conceptualization, Methodology, and biogeographical patterns, with a comprehensive list of species. Software, Data curation, Formal analysis, Writing – orig- Bulletin of the American Museum of Natural History, 431(13): 1‑163. inal draft, Visualization, Investigation. Writing – review Dagosta, F.C.P.; de Pinna, M.; Peres, C.A. & Tagliacollo, V.A. 2020. Existing & editing. All authors actively participated in the discus- protected areas provide a poor safety-net for threatened Amazonian fish sion of the results, and reviewed and approved the final species. Aquatic Conservation: Marine and Freshwater Ecosystems (special version of the paper. Authors declare no conflict of inter- issue), 1‑23. DOI est related to this paper. Dagosta, F.C.P.; Marinho, M. & Camelier, P. 2014. 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